• The Journal of Engineering Geology
• /
• v.6 no.3
• /
• pp.155-163
• /
• 1996

The current ASTM C227-90 is a prescription on the mortar-bar method. This recornrnends that mortar-bars should be made using a mixing ratio by weight of 675 grams aggregate to 300 grams cement, and their initial lengths should be measured in $24{\pm}2$ hours. This method emphasizes that the prepare sample mortar-bars and calculate expansion rates of them. This method requires constant G values (effective gauge lengths) of denominator in the calculation formula, which are fixed either at 10 inches or 250mm. This study, based on experimental approaches, reexamines the suggestions made by those two prescriptions above and important results are summarized in the following. 1. Not only alkali-aggregate reaction but also interaction of interstitial and gel water are responsible for expansion of mortar-bars. This requires partial modification of the current ASTM C227-90. 2. A mixing ratio by volume rather than by weight of aggregate to cement is recommendable for measuring the amount of expansion resulting from alkali-aggregate reaction and from interstitial water. 3. The method of when to measure initial lengths and how to calculate expansion rate suggested by ASThI C227-90 and Cl90-93a should partly be modified for more accurate results.

• The Journal of Engineering Geology
• /
• v.13 no.3
• /
• pp.309-320
• /
• 2003

Since the concrete covers most structures in modern architecture and it is composed of aggregates of about 75%, the appropriate selection of aggregates is valuable for the durability of concrete. A major cause of the expansion of mortar-bar measured by ASTM C 227-90 has been accounted by the alkali-aggregate reaction. This study carried out designed experiments on some aggregates including basalt and sandstone, to classify the expansion factors into the alkali-aggregate reaction, the increase of the gel pore volume, and the interstitial water that could expand physically the cracks or foliation developed in aggregates itself. The quantitative analyses of expansion by each factor indicated that the interstitial water and/or the alkali-aggregate reaction had major roles in the concrete expansion. Thus, if the supplied aggregates have deteriorated the structural framework, it is important to investigate the exact causes through this suggested method.